DESCRIPTION (from the applicant's abstract) The most significant etiological factor in Alzheimer's disease (AD) is age. But how does age contribute to the cellular and molecular pathology of AD? It is hypothesized that hippocampal neurons from aged animals are more susceptible to Abeta than younger neurons due to a decreased ability to generate the energy needed to control ion fluxes in this region of the AD brain. Novel techniques for the culture of aged neurons in serum-free medium have been developed recently by the PI, enabling examination of age-related cellular responses. New data have been obtained that subtoxic levels of lactate acidosis alter APP processing resulting in deposition of more amyloidogenic fragments. Also, neurons from aged rats are more susceptible to Abeta, lactate acidosis, and glutamate toxicity and fail to increase ATP levels to meet demands of increased ionic fluxes. Using neurons cultured from adult and aged rats, the first aim is to compare responses to fibrillar Abeta in terms of intracellular calcium, pH, and viability. Also regional AD pathology will be examined by comparing responses to Abeta in hippocampal with cerebellar granule neurons. The second aim examines the impact of glutamate and lactate acidosis on Abeta toxicity. The third aim examines whether age-related changes in susceptibility to Abeta are accounted for by declines in energy production, free radical damage, or induction of apoptosis. These studies hope to provide a better understanding of the age-related responses of cultured neurons to stressors thought to be important in the AD brain.